34_Defense_System

34_Defense_System - 0B X X X X X X X X X I I I V V V . . ....

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Unformatted text preview: 0B X X X X X X X X X I I I V V V . . . D D D e e e f f f e e e n n n s s s e e e S S S y y y s s s t t t e e e m m m 1B F F F u u u n n n c c c t t t i i i o o o n n n The function of the defense system is to recognize and destroy antigens. (Antigens are any substances your body recognizes as foreign.) The need for a defense system is obvious: the external environment actually penetrates our body. Because body cavities such as ears, guts, lungs, and vagina are all in contact with outside world, we are asking for trouble. 2B F F F i i i r r r s s s t t t L L L i i i n n n e e e o o o f f f D D D e e e f f f e e e n n n s s s e e e The first line of defense is fairly nonspecific. Consider the following list: skin: The skin is a tough tissue that protects internal, softer organs from the outside. It also has toxic fatty acids on its surface, which prevent fungal infection (no matter what your parents told you all those years, you should not wash dont take it seriously); cilia: The air we breathe is full of antigens, so the cilia of the bronchi are constantly filtering out any particles big enough to be stopped by them. Thick mucus excreted by goblet cells immobilizes foreign particles and flushes them up to be swallowed and dealt with by the digestive system;...
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34_Defense_System - 0B X X X X X X X X X I I I V V V . . ....

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